Low latency satellite communication relay network

ABSTRACT

Methods and systems for free space communication comprising one or more satellites that may provide a continuous communication link between two or more terminals are disclosed. A first satellite may be configured to send and/or receive data signals from a first terminal through a first link, and a second satellite may be configured to send and/or receive data from a second terminal through a second link. The first satellite and the second satellite may be coupled through a crosslink. The satellites and the terminals may be positioned at a minimum latitude threshold in order to take advantage of the decreasing circumference of the earth at increasing latitudes. The system and the method may comprise dividing the communication pathway between into a plurality of smaller segments, which when linked together approximate an optimal pathway for low latency and enable maintaining of higher bandwidth between the two terminals.

CLAIMS OF PRIORITY

This patent application is a continuation and claims priority from:

-   (1) U.S. provisional patent application No. 62/502,403, entitled    ‘Low latency satellite communication relay network’, filed May 5,    2017.-   (2) U.S. patent application Ser. No. 15/971,224, entitled ‘Low    latency satellite communication relay network’, filed May 4, 2018.

FIELD OF TECHNOLOGY

This disclosure relates generally to techniques for achieving lowlatency communication with free-space communication data relay betweentwo or more locations.

BACKGROUND

Traditionally, fiber optic cables are placed on the ocean floor toconnect multiple land masses, and are also known as submarine cables.These submarine cables can stretch for thousands of kilometerswithstanding harsh underwater environment, and may require multiplerepeaters and amplifiers to maintain data integrity from one end-pointto another. For example, the current state of the art in submarinecommunication cables includes the AC-1 cable from New York City toLondon, with an estimated round-trip latency of 64.8 ms. The latency ofintercontinental terrestrial, e.g., submarine, communication cables,however, is driven by the speed of light through fiber. The speed oflight through a fiber is roughly 2.044×10⁸ m/s. In contrast, the speedof light through the atmosphere, e.g., air, is roughly 2.989×10⁸ m/s,approximately 30% faster.

Several attempts have been made to establish a space-based lasercommunication network. Typically, such a network would be designedaround a backbone of LEO, MEO, and/or GEO satellites withinter-satellite links, and laser links to other spacecrafts and toairborne platforms and ground sites. Geostationary earth orbit (GEO)communication satellites have inherently high latency, and offercoverage of a reasonably large fraction of the Earth per satellite buthave long communication paths (altitude of 36,000 km) resulting in asignal latency of at least 120 ms per path. Additionally, GEO satellitesare generally restricted to radio frequency signals, which due toregulations limit available bandwidth to a range of hundreds of MHz to afew GHz. Furthermore, deploying GEO satellites is far more expensivethan deploying LEO or MEO satellites. Low earth orbit (LEO) satellitesare often deployed in satellite constellations. Because the coveragearea provided by a single LEO satellite only covers a small area thatmoves as the satellite travels at high angular velocity needed tomaintain its orbit, a plurality of LEO satellites are often needed tomaintain continuous coverage over a larger area. One benefit of usingLEO satellites is the ability to provide low latency broadbandtelecommunications compared to GEO satellites. Medium earth orbit (MEO)satellites may also provide a solution for overcoming the latencychallenge in GEO constellations. MEO is the region of space around theEarth above LEO (altitude of 2,000 km or less) and below geostationaryearth orbit.

Traditional satellite communication constellations are dedicated tomaximizing continuous end to end global coverage to reach as many usersaround the global, such as, e.g., Iridium, Globalstar, OneWeb, andLeoSat. While this constellation design is aimed for end-to-endcommunication from any point on the globe, and to ultimately serve manyusers to any other point, there are two inherent deficiencies with thisgeneralized approach. If two communication end-points are well knownthen this constellation design (1) does not achieve the minimum latencybetween two points of communication at the given altitude as needed forultra-low latency or real-time applications, such as, e.g., financialtransactions and robotic surgery, and (2) does not minimize thevariability in the maximum and minimum latencies between satellite tosatellite communication hand offs between satellites in different orbitsand at different orbit locations. Since terrestrial end point locationswould be undefined ahead of time in such a network, the system does nottake advantage of known variables, such as, e.g., geography, andweather. For example, with high frequency financial transactions,information asymmetry enables traders to outmaneuver the market and atrader who has knowledge of what the other markets are doing beforeother traders may obtain a benefit from such knowledge. Additionally,three quarters of the earth's surface is ocean, and populationdistribution is non-uniformed, therefore equal, uniform coverage of theglobe is inefficient. With the increasing need for low latency satellitecommunications, there is a persistent need in the art for a highlyefficient system and method for providing an extensible high bandwidthcommunication satellite network.

SUMMARY

In one aspect, the present invention discloses a system and a method forfree space communication comprising one or more satellites that mayprovide a continuous communication link between two or more terminals. Aconstellation of two or more satellites configured in a plurality oforbital planes may be disposed at predetermined distance and/or altitudeintervals and may be communicatively coupled to form a sequential andbi-directional pathway at a low earth orbit (LEO) or a medium earthorbit (MEO)—below the geostationary earth orbit (GEO) of approximately36,000 km. Data may travel between the terminals along the communicationpathway, forming a data relay. A first satellite may be configured tosend and/or receive data signals from a first terminal through a firstcommunication link, and a second satellite may be configured to sendand/or receive data from a second terminal through a secondcommunication link. The first satellite and the second satellite may becoupled through a communication crosslink. Further, additionalsatellites may be used to increase communication distances and/or tooptimize the pathway for high-bandwidth and low-latency data transfers.Although the present disclosure is related to a constellation ofsatellites, the invention is not so limited and those of ordinary skillin the art can recognize that it can be implemented with any type ofhigh-altitude platform, such as, e.g., atmospheric balloons, aerialvehicles or space vehicles.

In another aspect, the present invention discloses a system and a methodfor high bandwidth and low latency data transfer in a determined optimalpathway of a satellite constellation network. The system and the methodmay comprise dividing the communication path between two terminals intoa plurality of smaller segments, which when linked together approximatean optimal pathway for low latency between the two terminals and enablemaintaining of higher bandwidth between the two terminals. In order toachieve minimal variability in latency, the approximation of the optimalpathway may further be required to meet or exceed a minimum accuracythreshold, in addition to optimization of variable portions of the path,such as, e.g., variations in terrestrial to non-terrestrial transmissionlinks at each end of the communication path. The system may require atleast two non-terrestrial satellite nodes; however, additionalsatellites may further reduce latency and variability as a plurality ofsegments between intermediate nodes may allow for closer approximationof the optimal pathway between the nodes in communication with theterrestrial terminals. In other words, the accuracy and/or precision ofthe approximation of the optimal pathway and variability thereof may bedirectly proportional to the number of satellites in the constellation.In some embodiments, the optimal pathway may be the shortest path, suchas, e.g., a path resembling a straight line between two terminals. Inother embodiments, the optimal pathway may be a theoretical shortestpath, such as, e.g., a mapped path that takes into consideration thegeography data, shape data, and/or weather data of the earth. Inessence, by using a system and a method for piece-wise path optimizationthrough coordinating and synchronizing communications between satellitenodes, lower latency and variability in latency may be achieved.

In other aspects, the use of many smaller segments may enable a higherbandwidth through the pathway by allowing higher bandwidth to bemaintained within each segment. In essence, since bandwidth of a pathsegment operating at a constant transmitted power falls off as the pathsegment increases in length such that bandwidth is inverselyproportional to length, by using more short segments to create a path,the bandwidth across a multiple segment path can be maintained at ahigher level without the need for greater transmitted power.Furthermore, if each of these segments adds minimal latency to theoverall path being traversed, then the use of more short segments tomaintain high bandwidth does not significantly add to the latency orvariability of latency in traversing the communications path.

After the determination of an optimal pathway, the system and the methodof the present invention may comprise determining each satellite'strajectory, orientation and/or position relative to other satellites ofthe same constellation, such that the one or more transceivers and/orthe one or more antennas of the satellites are fixed in position and donot require adjusting or steering to communicate with neighboringsatellites. In some embodiments, the present invention is not so limitedand adjusting or steering of the one or more transceivers and/or one ormore antennas may provide proper alignment of the communication pathway.The determination of the satellite's trajectory, orientation and/orposition may be based on aligning with the closest approximation of theoptimal pathway between two target terminals. The satellites may then belaunched into orbit and their orbital positions coordinated such thatthey pass in the vicinity of the closest approximation of the optimalpathway, and therefore minimizing latency and variability in latencyduring data transfer. In some embodiments, the satellites may beconfigured to provide continuous communication coverage between two ormore terminals located at predetermined latitude. For example, to takeadvantage of the decreased circumference or radius of parallels oflatitude as approaching either the South Pole or the North Pole, e.g.,increasing absolute value of latitude, the satellites may communicate toterminals located at or above, e.g., 30-degrees in the north or southdirections.

In yet another aspect, the present invention discloses a system and amethod for establishing a communications pathway along a multi-linkfree-space path comprising continuously moving nodes that may be basedsolely on geographic location information of the source and destinationpoints, instead of information about nodes outside of the geographicregion of the free-space path or content or metadata, such as, e.g.,date, time, headers of the information content, destination addressinformation, and other information that may permit the destination to besearched, or which may require analysis or interpretation of theinformation content. The system and the method of the present inventionmay forward data onto the next satellite in an adjacent orbital plane inthe communication pathway until it reaches the last satellite, which maybe closest to the destination terminal, without analyzing informationabout satellites outside of the free-space path or without regard todetermining communication content.

In other words, data entering a geographically defined region in spaceat one satellite is simply retransmitted to the next satellite with onlysignal conditioning which avoids introduction of latency or signalpropagation delays from analysis of relative position information aboutthe satellites to determine the next node to receive the data and avoidsintroduction of latency or signal propagation delays from analysis ofsignal content, or transduction of the communications signal from oneelectromagnetic form into another electromagnetic form that introduceslatency or signal propagation delays as the data is passed on to thenext node in the geographically defined region in space, e.g., withinthe communication path or channel. This approach is used to reduce oreliminate delays introduced into a communications chain due totraditional processing of data to establish a routing path, such as,e.g., analyzing, interpreting, compressing, and encrypting or decryptingelements of the communications data to determine how to forward the dataalong the chain of moving nodes based on content in the data, e.g.,destination address information or such as analyzing relative positionsof satellites to determine if path changes are required based on changesin relative position. The data sequence may be amplified or the signalelectrically conditioned, such as, e.g. filtered to remove noise, but itis not processed in any fashion that evaluates or uses content to makedecisions. In addition, downlinking of the data being communicated tothe destination terminal from the last satellite may also be performedindependent of communication content or traffic information, and may bebased on the geographic location relative to the destination terminaland/or electromagnetic visibility of communication devices that are atthe destination.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments are illustrated by way of example and are notlimited to the figures of the accompanying drawings, in which, likereferences indicate similar elements.

FIG. 1A illustrates a communication relay system comprising a singlesatellite, and

FIG. 1B illustrates a communication relay system comprising a pluralityof satellites, according to at least one embodiment.

FIG. 2A illustrates a satellite constellation network, and FIG. 2Billustrates a satellite network topology of communication crosslinks,according to at least one embodiment.

FIG. 3A illustrates a plurality of satellites orbiting a plane aroundthe earth, and FIG. 3B shows a planet rotating about an axis and anorbital plane rotating about another axis, according to at least oneembodiment.

FIGS. 4A-B show a map view of optimal communication pathways to reducelatency and variability in latency overlaid with a coordinate's grid,according to at least one embodiment.

FIGS. 5A-B show a map view of optimal communication pathways to reducelatency and variability in latency overlaid with a coordinate's grid anda boundary box corresponding to the pathways, according to at least oneembodiment.

FIGS. 6A-B show a map view of a satellite constellation providingcommunication along optimal pathways to reduce latency and variabilityin latency, according to at least one embodiment.

FIGS. 7A-B show map views of a satellite constellation and multiple datapaths overlapping along an approximation of an optimal pathway,according to some embodiments.

FIGS. 8A-B show a map view of a satellite constellation providingcommunication along optimal pathways comprising various terminal types,according to at least one embodiment.

FIG. 9 is a schematic diagram of a satellite that may be implemented inat least one embodiment of the present invention.

FIG. 10 illustrates a communication payload that may be implemented inat least one embodiment of the present invention.

FIG. 11 is a diagram of a communications channel, according to at leastone embodiment.

FIG. 12 is a flowchart of a method for a communication networkcomprising one or more satellites, according to at least one embodiment.

FIGS. 13A-B depict flow diagrams for determining satellite datatransmission, according to at least one embodiment.

DETAILED DESCRIPTION

Disclosed are a system and a method for optimizing free-spacecommunication data relay between two or more locations for specificcommunications parameters such as, but not limited to, transit latencyand variability in transit latency. Although the present embodimentshave been described with reference to specific example embodiments, itwill be evident that various modifications and changes may be made tothese embodiments without departing from the broader spirit and scope ofthe various embodiments. In addition, the components shown in thefigures, their connections, couples, and relationships, and theirfunctions, are meant to be exemplary only, and are not meant to limitthe embodiments described herein.

In at least one embodiment, the present invention discloses a system anda method for free space communication comprising one or more satellitesthat may provide a continuous communication link between two or moreterminals. A constellation of two or more satellites configured in aplurality of orbital planes may be disposed at predetermined distanceand/or altitude intervals and may be communicatively coupled to form asequential and bi-directional pathway at a low earth orbit (LEO) or amedium earth orbit (MEO)—below the geostationary earth orbit (GEO) ofapproximately 36,000 km altitude. Data may travel between the terminalsalong the communication pathway, forming a data relay. A first satellitemay be configured to send and/or receive data signals from a firstterminal through a first communication link, and a second satellite maybe configured to send and/or receive data from a second terminal througha second communication link. The first satellite and the secondsatellite may be coupled through a communication crosslink. Further,additional satellites may be used to increase communication distancesand/or to optimize the pathway for high-bandwidth and low-latency datatransfers. Although the present disclosure is related to a constellationof satellites, the invention is not so limited and those of ordinaryskill in the art can recognize that it can be implemented with any typeof high-altitude platform, such as, e.g., atmospheric balloons, aerialvehicles or space vehicles.

FIG. 1A illustrates a communication relay system comprising a singlesatellite, according to at least one embodiment. Satellite 100 may be amember of a constellation of satellites that may be configured toprovide continuous coverage between geographic areas. Satellite 100 maybe communicatively coupled to terminal A 102 through communication linkA 104, and may also be communicatively coupled to terminal B 106 throughcommunication link B 108. Communication link A 104 and communicationlink B 108 may comprise bi-directional optical and/or radio frequency(RF) transmission pathways, such that data may travel from terminal A102 to terminal B 106, or vice versa. Additionally, data may be uplinkedand/or downlinked between satellite 100 and either terminal A 102 orterminal B 106 when there is electromagnetic visibility betweencommunicating elements of satellite 100 with the respective terminal.Distance 110 may be a distance between terminal A 102 and terminal B 106between which data travels, and may be limited by communicationvisibility.

Satellite 100 may comprise one or more uplink/downlink transceiverand/or one or more RF antenna to communicate with terminal A 102 andterminal B 106. Optical communication may be less susceptible tointerference and harder to jam than RF communication due to narroweroptical beam widths compared to radio frequency beam widths; however,optical communication may be more vulnerable to weather conditions, suchas moisture in the atmosphere that may scatter or distort optical waves,limiting data reliability. After data has reached an endpoint at eitherterminal A 102 or terminal B 106, it may then be delivered to an enduser location, such as, e.g., a financial services server or aterrestrial communication network.

Terminal A 102 and terminal B 106 may comprise one or more transceiversoperating in multiple frequencies, or a single frequency with differentpolarizations. Terminal A 102 and terminal B 106 may also comprise agimbal system or phased array for steering and tracking of individualsatellite communication links during each pass, and may be controlled bya server comprising a memory and a processor configured to maintaincontinuous connectivity between terminal A 102 and terminal B 106. Insome embodiments, terminals may be fixed terrestrial facilities, and mayalso be mobile, such as, e.g., a ground vehicle; airborne, such as,e.g., a manned or an unmanned aerial vehicle or a hot-air balloon;maritime, such as, e.g., an ocean vehicle or platform; and/orspace-based, such as, e.g., another satellite.

The communication relay system may comprise a control station 112communicatively coupled to a memory and a processor configured tocontrol lateral, vertical and rotational movements of satellite 100.On-board propulsion and attitude control systems of satellite 100 may beused to maintain optimal satellite orientation and position for reduceddata transfer latency. In some embodiments, control station 112 may notbe needed and control functions of satellite 100 may be embedded within.

FIG. 1B illustrates a communication relay system comprising a pluralityof satellites, according to at least one embodiment. Satellite A 150 maybe communicatively coupled to terminal A 152 through communication linkA 154. Satellite B 156 may be communicatively coupled to terminal B 158through communication link B 160. Satellite A 150 and satellite B 156may comprise one or more transceivers and/or one or more antennas andmay be communicatively coupled to each other through inter-satellitecrosslink 162. Crosslink 162 may provide bi-directional optical and/orRF transmission to form a complete pathway for data transfer betweenterminal A 152 and terminal B 158. The configuration in the presentfigure may permit wider separation of terminals compared to theconfiguration of FIG. 1A, such that distance 164 between terminal A 152and terminal B 158 is larger than that of distance 110 of FIG. 1A.

Although two satellites are shown in the present figure, any number ofsatellites can be employed in the communication system, in which case aplurality of inter-satellite crosslinks can be used to transmitinformation or data from satellite A 150 that receives uplink data fromterminal A 152 to satellite B 156 that sends downlink data to terminal B158. In addition, the communication relay system may be configured to bescalable and/or reconfigurable, such that individual satellites of aconstellation in orbit can be added, removed, re-oriented and/orre-positioned while maintaining continuous connectivity between terminalA 152 and terminal B 158. The system may also be configured to compriseextra or redundant satellite nodes or communication paths, such as usedto make new connections before old ones are dropped in order to maintaincontinuous connectivity as the satellites orbit around the earth.

In some embodiments, the inter-satellite crosslink 162, communicationlink A 154, and/or communication link B 160, whether comprising RF,optical, millimeter, terahertz and/or another wavelength, may comprise aplurality of different frequencies, or a single frequency with differentpolarizations used for sending and receiving data to preventtransmission interference or crosstalk. The plurality of wavelengths maybe used at the same time, in the same direction to achieve redundanttransmission affected differently by the space medium and/orinterference, to achieve better control and coordination betweensatellites, and/or to increase throughput or bandwidth of any of theinter-satellite links. Data transfer rate may be increased throughfrequency division multiplexing and/or differences in polarization whenemploying a plurality of wavelengths or polarizations in thecommunications channel.

The communication relay system may comprise a control station 166communicatively coupled to a memory and a processor configured tocontrol lateral, vertical and/or rotational movements of satellite A 150and satellite B 156. Onboard propulsion and attitude control systems ofsatellite A 150 and satellite B 156 may be used to maintain optimalsatellite orientation and/or position for reduced data transfer latency.In addition, control station 166 may determine an optimal data routingpath among a constellation of satellites based on current datacommunication loads through the network. In some embodiments, controlstation 166 may not be needed and control functions of satellite A 150and satellite B 156 may be embedded within the respective satellite. Forexample, satellite A 150 and satellite B 156 may autonomously monitorthemselves by communicating their statuses to each other and/or to otherneighboring satellites, and may route or select an appropriatecommunication path in real time.

FIG. 2A illustrates a satellite constellation network, according to atleast one embodiment. The network may comprise one or more satellite 200disposed in one or more near-polar orbital plane 202 orbiting the earth,and configured to transmit data between terminal A 204 and terminal B206 through bi-directional communication pathway 208. Orbital plane 202may permit satellite 200 to fly over specific areas at predeterminedtime intervals and predetermined terrestrial locations and, therefore,to connect terminal A 204 with terminal B 206 located at variouslocations around the world. Satellite 200 may be configured to receivean uplink signal from terminal A 204 when it is within electromagneticvisibility of terminal A 204, and may retransmit the signal to anothersatellite or to terminal B 206 when it is within electromagneticvisibility of the other satellite or terminal B 206.

In general, a plurality of satellite 200 may be separated by a distanceof 1,000 km or more. Due to the long range communication, satellite 200may comprise directional optical and/or RF transmission beams. The useof directional beams may require that the transmitter of thetransmitting satellite point at the receiver of the receiving satellite,and the receiver of the receiving device point at the transmitter of thetransmitting satellite. Such directional beams may comprise widths ofless than, e.g., 10-degrees for an RF transmission or less than, e.g.,one-degree for an optical transmission. Because the optical signal ishighly directional, multiple receiving telescopes can be co-locatedwithout interfering with one another. As the number of networksatellites in orbit increases, there will be an increasing probabilityof two (or more) satellites simultaneously passing within view of asingle terminal or ground station. With multiple receiving telescopes atany ground location, each can be trained on a different passing networksatellite. Since the communication channel is optical, the field of viewcan be quite small, allowing separate telescopes to track and receivedata from different satellites without interference.

The types of constellations that can be implemented is not limited tothe present exemplary embodiment, but can be extended to other types,such as, e.g., varying numbers of satellites, orbital planes, distancesbetween satellites, and/or orbital inclinations. The network may bescalable and reconfigurable such as by having the capability of addingsatellites to an existing constellation of satellites. This can be doneto replenish an outdated satellite, to increase coverage, and/or tocreate redundancy in the system. For example, a satellite can be addedinto an existing orbital plane and connected to neighboring satellitesby the transceiver's steering capability. In other embodiments, thepresent invention discloses a system and a method for configuring orreconfiguring satellite orientation and position in a constellation topermit directional transmissions without the use of any mechanicaladjusting or steering of the transceivers.

FIG. 2B illustrates a satellite network topology of communicationcrosslinks, according to at least one embodiment. A constellation ofsatellite 250 may be disposed in one or more orbital plane 252,communicatively coupled to neighbor satellites through inter-planecrosslink 254 and intra-plane crosslink 256. Intra-plane crosslink 256may comprise a communication pathway between two satellites in the sameorbital plane, and inter-plane crosslink 254 may comprise acommunication pathway between two satellites in different, and generallyjuxtaposed, orbital planes. Each inter-plane crosslink 254 andintra-plane crosslink 256 may comprise one or more transceivers foroptical data transmission and/or one or more antennas for RF datatransmission, and may be able to reach farther than the nearest neighborin any direction.

Although the present invention shows a 4×5 (four satellites by fiveplanes) configuration, any other configuration may be used, such as,e.g., 24×8. In addition, satellite 250 may comprise any amount ofinter-plane crosslink 254 and/or intra-plane crosslink 256, such as,e.g., more than four or less than four.

FIG. 3A illustrates a plurality of satellites orbiting a plane aroundthe earth, according to at least one embodiment. Satellite A 300 andsatellite B 302 may traverse orbital plane 304 to coordinate groundcoverage and to provide a data relay between two or more terminals. Theymay operate under shared control and may be synchronized such thatsatellite A 300 may perform the relay for a particular time interval perpass of a terminal with an overlap in coverage with satellite B 302,allowing for a continuous transmission between the terminals. SatelliteB 302 may trail satellite A 300 at predetermined distance, altitude,and/or time intervals, such that they are fixed in position relative andorientation to each other. In other embodiments, their relativepositions are not fixed and are varying. Satellite A 300 and satellite B302 may comprise an onboard server comprising a memory and a processorthat may allow the satellites to orbit autonomously in a fixedorientation and position. In addition, it may allow satellite A 300 andsatellite B 302 to change orientations and positions, such as, e.g., inorder to achieve and/or to maintain a desired orientation or position.

FIG. 3B shows a planet rotating about an axis and an orbital planerotating about another axis, according to at least one embodiment.Orbital inclination 350 may be an angle of orbital plane 352 in relationto reference plane 354 of the planet. As examples, an inclination ofzero-degrees may indicate an orbital plane traveling parallel to areference plane traveling in a generally east direction (referred to asprograde); an inclination of 90-degrees may indicate an orbital planethat is perpendicular to the reference plane and traveling in agenerally north direction on one side of the earth and a generally southdirection on the other side of the earth; an inclination of 180-degreesmay indicate an orbital plane traveling parallel to the reference planeand in a generally west direction (referred to as retrograde); and aninclination of 270-degrees may indicate an orbital plane that isperpendicular to the reference plane and traveling in a generally southdirection on one side of the earth and a generally north direction onthe other side of the earth, or opposite of the direction of the90-degree inclination. In some embodiments, reference plane 354 may bethe equator of the earth.

In some embodiments, an orbital plane of a constellation of satellitesmay be configured to take advantage of decreasing radius of the earth atincreasing latitudes in the north and south directions away from theequator, to reduce communication crosslink distances and distancevariabilities, and hence to reduce data transfer latency and variabilityin latency. The circumference of the earth may be inversely proportionalto the latitude such that a high latitude corresponds to a low radius ofthe circumference of the earth. For example, the constellation may beconfigured to provide communication coverage between two or moreterminals by directing data north or south above a predetermined minimumlatitude, such as, e.g., 45-degrees, to take advantage of the smallercircumference of parallels of the planet at a higher latitude.

In at least one embodiment, the present invention discloses a system anda method for determining an optimal pathway of a satellite constellationnetwork. The system and the method may comprise dividing thecommunication path between two terminals into a plurality of smallersegments, which when linked together approximate the optimal pathway,for example, to minimize latency and variability in latency, and/or toincrease bandwidth along the communication paths. In order to achieveminimal variability in latency, the approximation of the optimal pathwaymay further be required to meet or exceed a minimum accuracy threshold,in addition to optimization of variable portions of the path, such as,e.g., variations in terrestrial to non-terrestrial transmission links ateach end of the communication path. The system and the method maycomprise dividing the communication path between two terminals into aplurality of smaller segments, which when linked together enablemaintaining of low latency between the terminals. The system may requireat least one non-terrestrial satellite node; however, additionalsatellites may further reduce latency and variability as a plurality ofsegments between intermediate nodes may allow for closer approximationof the optimal pathway between the nodes in communication with theterrestrial terminals, in addition to shortening communication distancesbetween the nodes which may permit data transfer of higher bandwidths.In other words, the accuracy and/or precision of the approximation ofthe optimal pathway may be directly proportional to the number ofsatellites in the constellation. In some embodiments, the optimalpathway may be the shortest path, such as, e.g., a path resembling astraight line between two terminals. In other embodiments, the optimalpathway may be a theoretical shortest path, such as, e.g., a mapped paththat takes into consideration the geography data, shape data, and/orweather data of the earth. In essence, by using a system and a methodfor piece-wise approximation to path optimization through coordinatingand synchronizing communications between satellite nodes, lower latencyand variability in latency may be achieved.

The use of many smaller segments may enable a higher bandwidth throughthe pathway by allowing higher bandwidth to be maintained within eachsegment. Since bandwidth of a path segment operating at a constanttransmitted power falls off as the path segment increases in length suchthat bandwidth is inversely proportional to length, by using more shortsegments to create a path, the bandwidth across a multiple segment pathcan be maintained at a higher level without the need for greatertransmitted power. Furthermore, if each of these segments adds minimallatency to the overall path being traversed, then the use of more shortsegments to maintain high bandwidth does not significantly add to thelatency or variability of latency in traversing the communications path.

After the determination of an optimal pathway, the system and the methodof the present invention may comprise determining each satellite'strajectory, orientation and/or position relative to other satellites ofthe same constellation, such that the one or more transceivers and/orthe one or more antennas of the satellites are fixed in position and donot require adjusting or steering to communicate with neighboringsatellites. In some embodiments, the present invention is not so limitedand adjusting or steering of the one or more transceivers and/or one ormore antennas may provide proper alignment of the communication pathway.The determination of the satellite's trajectory, orientation and/orposition may be based on aligning with the closest approximation of theoptimal pathway between two target terminals. The satellites may then belaunched into orbit and their orbital positions coordinated such thatthey pass in the vicinity of the closest approximation of the optimalpathway, and therefore minimizing latency and variability in latencyduring data transfer. In some embodiments, the satellites may beconfigured to provide continuous communication coverage between two ormore terminals located at predetermined geographic locations relative toeach orbital plane through a route that deviates from an arc between thetwo terminals. For example, to take advantage of the decreasedcircumference or radius of parallels of latitude as approaching eitherthe South Pole or the North Pole, e.g., increasing absolute value oflatitude, the satellites may only provide coverage for terminals incertain latitude regimes by routing traffic into a cross-planecommunications path located at or above, e.g., 30-degrees in the northor south directions.

FIGS. 4A-B show a map view of optimal communication pathways to reducelatency and variability in latency overlaid with a coordinate's grid,according to at least one embodiment. In FIG. 4A, land mass A 400 andland mass B 402, comprising terminal A 404 and terminal B 406respectively, may be separated by a geographic barrier, such as, e.g.,an ocean. The optimal pathway between terminal A 404 and terminal B 406may be straight line 408, representing an arc between the two terminalsthat does not intersect the surface of the earth. Straight line 408 maybe a line segment with endpoints located at terminal A 404 and terminalB 406, and may be the shortest distance between the two terminals. Inorder to achieve the lowest latency possible, the actual communicationlink may mimic straight line 408. Satellites of a constellation may becoordinated to transmit data from one plane to the next, which iseffectively a straight communication pathway across multiple planes. Insome embodiments, mimicry of straight line 408 does not compriseterminal A 404 and terminal B 406 where data is uplinked or downlinked.In other embodiments, mimicry of straight line 408 does compriseterminal A 404 and terminal B 406.

In FIG. 4B, the optimal pathway between terminal A 450 of land mass A452 and terminal B 454 of land mass B 456 may be theoretical pathway458. Theoretical pathway 458 may be a charted or mapped pathway betweenterminal A 450 and terminal B 454 that may be the shortest path whentaking into consideration the geography and topology of the earth'ssurface or shape. One or more theoretical pathway 458 may be determinedor identified and stored in a database coupled with a memory and aprocessor. When two ground locations are chosen on a map, the processormay determine the shortest theoretical pathway based on recordedinformation within the database. In order, for example, to achieve thelowest latency possible, the actual communication link may mimictheoretical pathway 458. Theoretical pathway 458 may comprise aplurality of line segments connected at one or more vertex 460, whereinthe vertex represents a change in direction or passing along of datathrough a satellite node.

In addition, theoretical pathway 458 may comprise one or more segmentswith data traveling generally in the north or south directions, e.g.,the change in the north-south direction is greater than the change inthe east-west direction below a predetermined latitude or minimumthreshold latitude, e.g., below 30-degrees, such that the latitudechanges faster than the longitude from one point to the next intraversing the pathway.

On the other hand, the two terminal segments of theoretical pathway 458closest to terminal A 450 and terminal B 454 may generally travel in theeast or west directions when at a predetermined latitude, e.g.,30-degrees or above, such that longitude changes faster than latitudefrom one point to the next. The one or more middle sections may belonger, separately or cumulatively, in distance than the terminalsections. This permits theoretical pathway 458 to take advantage of thefact that the circumference of the parallels of latitude may bedecreasing at higher latitudes by avoiding traveling east and west atlower latitudes as much as possible.

In some embodiments, theoretical pathway 458 may not be located near apredetermined minimum latitude threshold, e.g., 30-degrees or above, andmay comprise terminal segments generally traveling in the east or westdirection only where the theoretical pathway 458 is highest in latitude.For example, if theoretical pathway 458 stays within 20-degrees latitudein its entirety, then an algorithm coupled with a memory and a processormay determine that sections generally traveling in the east and westdirections may only begin where theoretical pathway 458 is above apredetermined minimum latitude threshold and within the upper latituderange, e.g., 15- to 20-degrees.

FIGS. 5A-B show a map view of optimal communication pathways to reducelatency and variability in latency overlaid with a coordinate's grid anda boundary box corresponding to the pathway, according to at least oneembodiment. In FIG. 5A, the shortest path between terminal A 500 of landmass A 502 and terminal B 504 of land mass B 506 may be straight line508. Boundary box 510 may be an algorithm-generated shape comprisingmaximum and minimum latitudes and longitudes within which data transfersbetween terminal A 500 and terminal B 504 are permitted. The area ofboundary box 510 may be a cumulative of all possible integratedcommunication paths that approximate straight line 508 and may liewithin the maximum and minimum latitudes and longitudes. The edges ofbox 510 may be the longest paths permitted, and may surround straightline 508, which may be the shortest path, and may be predetermined asthe satellites may be configured to orbit in a predictable pattern. Forexample, from every point on straight line 508, there may be positiveand negative maximum latitudes, e.g., 20-degrees in the north directionand 20-degrees in the south direction, and longitude, e.g., 30-degreesin the west direction and 30-degrees in the east direction, for datatransfer to occur. In general, the farther away from straight line 508,the higher the latency of the communication path, such that deviation tostraight line 508 within box 510 is directly proportional to latency,e.g., a larger distance will correlate with higher latency. On the otherhand, the longitudinal boundaries of box 510 may be constant and equalto the longitudes of terminal A 500 and terminal B 504, since datacommunication may not occur beyond the positions of the terminals. Insome embodiments, the longitudinal boundaries of box 510 may extend tothe west or east of the terminals, since the communication segmentsbetween the last satellites in a pathway may allow communications to theterminals from locations east and or west of the terminals, not just atthe same longitudes of the terminals.

As more satellites and orbital planes are added to the constellation,the latitude edges of box 510 may shrink and approach straight line 508until it matches straight line 508. The amount of satellites in theconstellation, or the amount of satellites in an effective area of apart of the constellation, may be inversely proportional to size of box510 such that a large number of satellites may correlate with a smallsize, and vice versa. The effective area may be a predetermined areaaround the optimal pathway and may comprise a varying amount ofsatellites at any given time, such that the size of box 510 is dynamicand changing in real-time. An algorithm may determine the minimum amountof satellites needed to match the latitude edges of box 510 to straightline 508. When satellite and orbital plane density is increased, therewould be a larger number of satellites in the constellation, andtherefore, distance and time intervals of communication hand-oversbetween satellites of neighboring orbital planes may be decreased whilehand-over frequency is increased, until a saturation point is reachedand beyond, which there is a decrease in bandwidth or increase inlatency of the system as more satellites are added.

In FIG. 5B, the shortest path between terminal A 550 of land mass A 552and terminal B 554 of land mass B 556 may be theoretical pathway 558.Boundary box 560 may be an algorithm-generated shape comprising maximumand minimum latitudes and longitudes within which data transfers betweenterminal A 550 and terminal B 560 are permitted. The area of boundarybox 560 may be a cumulative of all possible integrated communicationpaths that approximate theoretical pathway 558 and may lie within themaximum and minimum latitudes and longitudes. The edges of box 560 maybe the longest path, and may surround theoretical pathway 558, which maybe the shortest path, and may be predetermined as the satellites orbitin a predictable pattern. For example, from every point on theoreticalpathway 558, there may be positive and negative maximum latitudes, e.g.,20-degrees in the north direction and 20-degrees in the south direction,and longitude, e.g., 30-degrees in the west direction and 30-degrees inthe east direction, for data transfer to occur. In general, the fartheraway from theoretical pathway 558, the higher the latency of thecommunication path, such that distance to theoretical pathway 558 withinbox 560 is directly proportional to latency, e.g., a larger distancewill correlate with higher latency. On the other hand, the longitudinalboundaries of box 560 may be constant and equal to the longitudes ofterminal A 550 and terminal B 554, since data communication may notoccur beyond the positions of the terminals. In some embodiments, thelongitudinal boundaries of box 560 may extend to the west or east of theterminals, since the communication segments between the last satellitesin a pathway may allow communications to the terminals from locationseast and or west of the terminals, not just at the same longitudes ofthe terminals.

As more satellites and orbital planes are added to the constellation,the latitude edges of box 560 may shrink and approach theoreticalpathway 558 until it matches theoretical pathway 558. The amount ofsatellites in the constellation, or the amount of satellites in aneffective area of a part of the constellation, may be inverselyproportional to size of box 560 such that a large number of satellitesmay correlate with a small size, and vice versa. The effective area maybe a predetermined area around the optimal pathway and may comprise avarying amount of satellites at any given time, such that the size ofbox 560 is dynamic and changing in real-time. An algorithm may determinethe minimum amount of satellites needed to match the latitude edges ofbox 560 to theoretical pathway 558. When satellite and orbital planedensity is increased, there would be a larger number of satellites inthe constellation, and therefore, distance and time intervals ofcommunication handovers between satellites of neighboring orbital planesmay be decreased while the frequency of hand-overs is increased.

FIGS. 6A-C show map views of a satellite constellation providingcommunication along optimal pathways to reduce latency and variabilityin latency, according to at least one embodiment. In FIG. 6A, theshortest path between terminal A 600 of land mass A 602 and terminal B604 of land mass B 606 may be optimal pathway 608. Optimal pathway 608may be a straight line segment or a theoretical pathway comprising aplurality of line segments. A constellation of satellite 610 may bedisposed in one or more evenly spaced orbital plane 612, and may beconfigured to provide bi-directional communication between terminal A600 and terminal B 604 along optimal pathway 608. The constellation ofsatellite 610 in FIG. 6A may be fixed at predetermined distance,altitude, and/or time intervals, such that they are fixed in positionrelative and orientation to each other, permitting for the synchronizedarrival of one or more assigned satellite 610 along optimal pathway 608at a predetermined time. Satellite 610 may comprise an onboard servercomprising a memory and a processor that may allow it to orbitautonomously in a fixed orientation and position relative to the othersatellites of the constellation. In another embodiment, both thesatellites 610 moving away from the optimal pathway 608 and the trailingsatellite 610 may both be in the communications beam at the same timesuch that during their overlapping time in the beam both may continue topass along the data without data link interruption.

Satellite 610 that is positioned closest to terminal A 600 may receivean uplink data transmission from terminal A 600, and may retransmit thedata to the closest satellite 610 located at an adjacent orbital plane612, effectively coordinating a straight inter-satellite communicationpath across multiple planes. Satellite 610 positioned closest toterminal B 604 may receive the data from an adjacent satellite 610 andmay retransmit the data to terminal B 604 through a downlinktransmission. Additionally, as each satellite 610 receives and transmitsdata along the data relay and then continues on its path on orbitalplane 612 away from optimal pathway 608, another satellite 610 in thesame orbital plane 612 may take its place to receive and transmit dataalong optimal pathway 608. The system may be configured such that asubsequent satellite 610 forms a new connection with another satellite610 of a different orbital plane 612 or forms a new uplink/downlinkconnection with terminal A 600 or terminal B 604 before any previousconnections are dropped from the preceding satellite 610 in order tomaintain continuous connectivity as the constellation orbits and shiftsin position relative to the earth. In other words, data may be handedover from the satellite 610 moving away from optimal pathway 608 to atrailing satellite 610 of the same orbital plane 612 through aninter-satellite crosslink in the same plane prior to disconnecting fromthe data relay.

In FIG. 6B, the shortest path between terminal A 650 of land mass A 652and terminal B 654 of land mass B 656 may be optimal pathway 658.Optimal pathway 658 may be a straight line or a theoretical pathcomprising a plurality of line segments. A constellation of satellite660 may be disposed in one or more evenly spaced orbital plane 662, andmay be configured to provide bi-directional communication betweenterminal A 650 and terminal B 654 along optimal pathway 658. Theconstellation of satellite 660 in FIG. 6B may vary in distance,altitude, and/or time intervals, such that they are not fixed inposition relative to each other, and their arrival along optimal pathway608 varies in time.

Satellite 660 positioned closest to terminal A 650 may receive an uplinkdata transmission from terminal A 650, and may retransmit the data tothe next closest satellite 660 located at an adjacent orbital plane 662,effectively coordinating an inter-satellite communication path acrossmultiple planes. Satellite 660 positioned closest to terminal B 654 mayreceive the data from an adjacent satellite 660 and may retransmit thedata to terminal B 654 through a downlink transmission. Additionally, aseach satellite 660 receives and transmits data along the data relay andthen continues on its path on orbital plane 662 away from optimalpathway 658, another satellite 660 in the same orbital plane 662 maytake its place to receive and transmit data along optimal pathway 658.The system may be configured such that a subsequent satellite 660 formsa new connection with another satellite 660 of a different orbital plane662 or forms a new uplink/downlink connection with terminal A 650 orterminal B 654 before any previous connections are dropped from thepreceding satellite 660 in order to maintain continuous connectivity asthe constellation orbits and shifts in position relative to the earth.In other words, data may be handed over from the satellite 660 movingaway from optimal pathway 658 to a trailing satellite 660 of the sameorbital plane 662 through an inter-satellite crosslink in the same planeprior to disconnecting from the data relay. In another embodiment, boththe satellites 660 moving away from the optimal pathway 658 and thetrailing satellite 660 may both be in the communications beam at thesame time such that during their overlapping time in the beam both cancontinue to pass along the data without data link interruption.

Boundary box 664 may be an algorithm-generated shape indicating maximumand minimum latitudes and longitudes to permit data transfer betweenterminal A 650 and terminal B 654. The area of boundary box 664 may be acumulative of all possible integrated communication paths thatapproximate optimal pathway 658 and may lie within the maximum andminimum latitudes and longitudes. The edges of box 664 may be thelongest path, and may surround optimal pathway 658 which may be theshortest path, and may be predetermined by satellite orbits as thesatellites move in a predictable pattern. The system may be configuredto transmit data from satellite 660 to another satellite 660 of anadjacent orbital plane 662 in the direction of data flow as it movesinto position when one or more transceivers and/or one or more antennasof both the transmitting satellite 660 and the receiving satellite 660are within the edges of box 664. However, due to the constellationpossibly comprising non-fixed or varied satellite movements, datatransmission may occur when the satellites are within box 664 andpreferably along optimal pathway 558 or a close approximation, such asdepicted in FIG. 6A.

An adaptive algorithm of the system may determine the optimal pathway totransmit data to the next satellite 660 of an adjacent orbital plane 662if there are more than one viable option based on, e.g., relativeposition and orientation, deviation from the optimal pathway, distanceand/or electromagnetic visibility of the receiving satellite 660 and thetransmitting satellite 660, and saturation or congestion of thecommunication path. For example, there may be a maximum thresholddistance between a pair of satellite 660, at which point beyondtransmission may not be possible. In addition, electromagneticvisibility may depend on electromagnetic interference, atmosphericcontent or debris and the presence of clouds or adverse weatherconditions for platforms resident in the atmosphere or space and maydepend on electromagnetic interference or other space effects forplatforms in space. Relative positions and orientations of thecommunicating satellites may ideally be in a state to properly transmitand receive a signal. As such, only the satellites in orbital locationsthat most approximates optimal pathway 658 are used when predeterminedconstraints and parameters are met. In addition or alternatively, eachsurrounding receiving satellite 660 may comprise a value coinciding withwhether to establish connection with the transmitting satellite 660, andwhich may be based on, e.g., relative position and orientation,deviation from the optimal pathway, distance, electromagneticvisibility, and/or saturation or congestion of the communication path.Deviation from the optimal pathway may in part be determined by distancebetween the pair of satellite 660.

Actual path 666 may be the communication pathway that is taken by thesystem and the method, and may have been determined by the optimizationalgorithm. Actual path 666 may be the most accurate approximation ofoptimal pathway 658 by the satellites at any given time. In someembodiments, it may be preferred actual path 666 comprise the maximumnumber of satellites possible, such as a saturation point prior to adecrease in bandwidth or increase in latency from the possiblecomplexity in the system, e.g., to meet or exceed a predeterminedminimum communication distance threshold, in order to take advantage ofthe piece-wise network configuration, while minimally deviating fromoptimal pathway 658.

As more satellites and orbital planes are added to the constellation,the edges of box 664 may shrink and approach optimal pathway 658 untilit matches optimal pathway 658. The amount of satellites in theconstellation, or the amount of satellites in an effective area of apart of the constellation, may be inversely proportional to size of box664 such that a large number of satellites may correlate with a smallsize, and vice versa. The effective area may be a predetermined areaaround the optimal pathway and may comprise a varying amount ofsatellites at any given time, such that the size of box 664 is dynamicand changing in real-time. An algorithm may determine the minimum amountof satellites needed to match the latitude edges of box 664 to optimalpathway 658. When satellite and orbital plane density is increased,there would be a larger number of satellites in the constellation, andtherefore, distance and time intervals of communication hand-oversbetween satellites of neighboring orbital planes may be decreased whilethe frequency of hand-overs is increased.

In at least one embodiment, data may be sent along multiple paths thatapproximate optimal pathway 608 so that handovers between the satellitesin the same plane are not necessary. In such situation, overlapping dataor duplicate data reaching the destination terminal is processed out ofthe data stream by the receiving satellite or terminal so that latencyis not increased in the space portion of the pathway. The types ofconstellations that can be implemented is not limited to the presentexemplary embodiment, but can be extended to other types. For example,spacing of orbital planes may in some constellations be evenly spaced,while other constellations may not be evenly spaced. And in someconstellations the inclination of the planes may all be the same, whilein other constellations the inclinations of the planes may be varying.

FIGS. 7A-B show map views of a satellite constellation and multiple datapaths overlapping along an approximation of an optimal pathway,according to some embodiments. In FIG. 7A, a satellite constellation mayprovide communication overlap along an approximation of an optimalpathway, according to at least one embodiment. The shortest path betweenterminal A 700 of land mass A 702 and terminal B 704 of land mass B 706may be optimal pathway 708. Optimal pathway 708 may be a straight lineor a theoretical path comprising a plurality of line segments. Aconstellation of satellite 710 may be disposed in one or more evenlyspaced orbital plane 712, and may be configured to providebi-directional communication between terminal A 700 and terminal B 704along the best approximation to optimal pathway 708 represented bycommunication path A 714. Coverage overlap is provided by alternatepaths such as would exist when the data being communicated is sent alongone or more additional communication paths sharing some or none ofsatellite 710 along each path between terminal A 700 and terminal B 704.By providing two or more redundant pathways˜communication path B 716 andcommunication path C 718˜with identical content, such overlap mayprotect from noise, provide confirmation of data, provide an analyticalapproach to increasing data throughput from terminal A 700 to terminal B704, and avoid gaps in transmission. Coverage overlap may be provided bytwo or more transmission beams along the same communication path thatare identical in content but different in frequency or polarization, orare encoded differently so that they are affected differently by passagethrough the region of space.

FIG. 7B shows a partial communication overlap with a transmission signalbeing sent along two different paths through satellite nodes in the sameorbital plane at the start of a transmission. That is, data transmissionbetween terminal A 724 and terminal B 726 may travel along anapproximation of an optimal pathway, and overlap along only a portion ofthe distance between terminal A 724 and terminal B 726. The portion ofthe distance may be a beginning portion, a middle portion, and/or an endportion of the transmission. Terminal A 724 may transmit data tomultiple satellite nodes of an orbital plane 722 as each node engagesand disengages based on electromagnetic visibility to terminal A 724.Generally, a leading node that becomes visible to terminal A 724 may bethe first to initiate transmission or reception of data with terminal A724 prior to a trailing node becoming visible to terminal A 724 at alater time. The satellite constellation, and particularly the nodes ofan orbital plane, may be configured such that two nodes can receivetransmission from terminal A 724 for a portion of the time thesatellites are both electromagnetically in view. During the time whentwo nodes are in view, duplicate data to or from terminal A 724 maytravel along two paths simultaneously to reach the two (or more)respective nodes in view.

In the next series of data transmissions, the two initial nodes maysequentially transmit data along a northern path and a southern paththat may converge towards the optimal pathway to a single node (asshown), wherein the two data transmissions may comprise an overlapregion 728. Overlap region 728 may be a region that covers both signalpaths until they meet at the single node, and may encompass the contentas duplicate data. By providing redundancy in the data transmissionchannel, overlap may protect from noise, provide confirmation of data,provide an analytical approach to increasing data throughput fromterminal A 724 to terminal B 726, and avoid gaps in transmission.

In some embodiments, terminals of communication pathways may not berestricted to fixed terrestrial facilities, and may also be mobile, suchas, e.g., a ground vehicle; airborne, such as, e.g., a manned or anunmanned aerial vehicle or a hot-air balloon; maritime, such as, e.g.,an ocean vehicle or platform; and/or space-based, such as, e.g., anothersatellite. In one example, a ground user may wish to communicate to aGEO asset (geosynchronous platform) that he may not be located beneath.In this case, we have again two communications channel endpoints thatare geographically constrained˜the user to his ground location, and thegeosynchronous satellite to the orbital location that gives it an earthfootprint that is different and distinct, e.g., at some distance, fromwhat the ground user can see. For instance, say it is a GEO asset on theother side of the planet, or for a polar user (north or south poles), aGEO asset overlooking a more southerly or northerly latituderespectively than he can see, e.g., the equator. In any such case, thenetwork path would be defined by a bounding box constrained at one endby the user's geographic location, and at the other end by the GEOassets ground footprint (also a geographically defined reference). Inthis case, the communication would be from ground to space when aconstellation satellite reaches the user, e.g., enters the bounding boxwhere they can communicate with the user, and the communication at theother end of the bounding box would be up to a higher location in space,e.g., to the GEO asset, when a constellation satellite enters that partof the bounding box.

In another example, two geosynchronous assets may not comprisecommunication crosslinks, and their only path to the ground is typicallythrough terrestrial ground stations. If one of those stations were forsome reason not able to communicate, information could not be passedfrom one geosynchronous satellite to the other using terrestrialnetworks to span the distance between their different ground-based footprints. This may be resolved by instead communicating to a separatenetwork constellation from one of the two geosynchronous satellites,wherein the separate network constellation may communicate with theother of the two geosynchronous satellites. The communications to theseparate network by the two geosynchronous satellites would be definedwithin a bounding box defined by each GEO satellite's footprint, again afeature that is geographically defined, but communications would not beto the ground in either case, but only between space objects.

FIGS. 8A-B show a map view of a satellite constellation providingcommunication along optimal pathways comprising various terminal types,according to at least one embodiment. In FIG. 8A, the shortest pathbetween mobile device 800 of user 802 and terminal 804 may be optimalpathway 806. Optimal pathway 806 may be a straight line or a theoreticalpath comprising a plurality of line segments. A constellation ofsatellite 808 may be disposed in one or more evenly spaced orbital plane810, and may be configured to provide bi-directional communicationbetween mobile device 800 and terminal 804 along optimal pathway 806.Actual path 812 may be the path taken by the system and the method, andmay be the most accurate approximation of optimal pathway 806 at anygiven time that is based on satellite availability. In some embodiments,it may be preferred actual path 812 comprise the maximum number ofsatellites possible in order to take advantage of the piece-wise networkconfiguration, while minimally deviating from optimal pathway 806.

In FIG. 8B, the shortest path between satellite A 850 satellite B 852may be optimal pathway 854. Optimal pathway 854 may be a straight lineor a theoretical path comprising a plurality of line segments. However,satellite A 850 and satellite B 852 may not comprise a transmissioncrosslink for uni- or bi-directional communication. Satellite C 854 of aseparate network constellation may be able to link satellite A 850 andsatellite B 852 through actual path 856. The present example embodimentmay not comprise any ground or terrestrial platforms.

FIG. 9 is a schematic diagram of a satellite that may be implemented inat least one embodiment of the present invention. The satellite may be amember of a constellation of other satellites that may be configured toprovide continuous coverage to a predetermined area between two or moreterminals, and may comprise a central body 900. Body 900 may house aservice module and/or a communications payload. The communicationspayload may comprise a space to ground communications antenna 904 andinter-satellite link 906. One or more antenna 904 may comprise anyshape, such as, e.g., a helical shape, and may be maintained to point ata terminal on the earth's surface for RF data transmission. In someembodiments, the satellite may be configured to communicate with theterminal by optical data transmission using the satellite's one or moretransceivers. The terminal may comprise a plurality of up/down-linktelescopes and/or antennas such that new connections can be establishedbefore the old one is broken, as the satellite constellation passes theground site.

The service module may comprise a structural subsystem configured toprovide a mechanical base structure and to shield internal circuitryfrom extreme temperature changes, the ambient environment, radiationeffect and/or micrometeorite damage; a telemetry subsystem configured tomonitor onboard equipment operations, transmits equipment operation datato the earth control station, and/or receive the control station'scommands to perform equipment operation adjustments; a power subsystemcomprising one or more batteries coupled to solar panel 902 configuredto supply power to other satellite subsystems; a thermal controlsubsystem configured to protect electronic equipment from extremetemperatures due to internally produced heat, external solar heat, andthe freezing temperatures due to lack of sunlight exposure on differentsides of central body 900; and an attitude and orbit control subsystemcomprising attitude and orbit control sensors and actuators, e.g.,propulsion mechanisms such as small rocket thrusters, configured tomaintain the satellite in a predetermined orbital orientation andposition, in addition to maintaining direction of the one or moreantenna 904.

FIG. 10 illustrates a communication payload that may be implemented inat least one embodiment of the present invention. The payload maycomprise inter-satellite link 1000 disposed at an exterior portion of asatellite for inter-satellite intra- and inter-plane communications.Inter-satellite link 1000 may comprise one or more transceivers foroptical data transmission and reception, and/or one or more antennas forRF data transmission and reception. The transceivers and/or antennas maybe configured to be adjustable or steerable, such as, e.g., forcalibration with neighboring satellites or for establishing newcommunication paths such as when a new satellite is launched into orbit.In some embodiments, one or two nearest neighboring satellites may beutilized for inter-satellite intra- and inter-plane communications. Beamsteering may be used to compensate for satellite jitter and slight orbitvariations. Vertical link 1002 may be configured to communicate with aterminal through an uplink and/or a downlink connection, and may also beadjustable and/or steerable, such as, e.g., comprising a gimbal orelectronically steered phased array to track a terminal. Vertical link1002 may also comprise one or more transceivers for optical datatransmission and reception, and/or one or more antennas for RF datatransmission and reception, and may be disposed on the exterior of thesatellite. Circuit 1004 may comprise a processor and memory configuredfor receiving, transmitting, filtering, processing, amplifying and/orswitching data signals. In some embodiments, circuit 1004 may beconfigured to only receive and transmit data signals, but to not filter,process, amplify or switch data signals. In other embodiments,inter-satellite link 1000 and vertical link 1002 may not be adjustableor steerable, such that they are fixed in position.

FIG. 11 is a diagram of a communications channel, according to at leastone embodiment. Source 1100 may be a terminal, such as, e.g., a groundstation, an airborne vessel, a maritime vessel, or a mobile device, andmay transmit data to transceiver A 1102 of communication payload A 1104of satellite A 1106. The data may comprise a plurality of signalsassigned to specific frequencies within a designated frequency band andmultiplexed into a wavelength division multiplex signal. The wavelengthdivision multiplex signal may substantially increase transmission rateby using a plurality of channels, each transporting a part of theinformation to be transmitted. The signal may not require to beconverted to electrical signals such that it is simply traveling througha direct pipeline and changes its direction towards a destination.Transceiver A 1102 may retransmit the signal to transceiver B 1108 ofcommunication payload B 1110 of satellite B 1112 without performing anytype of analyzation or processing of the data.

FIG. 12 is a flowchart of a method for a communication networkcomprising one or more satellites. Operation 1210 determines startingand ending terminal locations for transferring data from and to. Theterminals may be positioned at a predetermined minimum latitude in orderto take advantage of the decreasing circumference of the earth atincreasing latitudes. Terminals may be fixed terrestrial facilities suchas a ground terminal, and may also be mobile, such as, e.g., a groundvehicle; airborne, such as, e.g., a manned or an unmanned aerial vehicleor a hot-air balloon; maritime, such as, e.g., an ocean vehicle orplatform; and/or space-based, such as, e.g., another satellite.Operation 1220 determines an optimal pathway based on, e.g., relativeposition and orientation, distance and/or electromagnetic visibility ofthe receiving satellite and the transmitting, and saturation orcongestion of the pathway. The optimal pathway may be a straight line ora theoretical pathway between the terminals. Operation 1230 divides theoptimal pathway into a plurality of smaller segments, which when linkedtogether approximates the optimal pathway for low latency data transferbetween the terminals. Operation 1240 configures the constellation inposition, orientation, and trajectory to approximate the smallersegments and to permit directional transmissions without the use of anymechanical adjusting or steering of the transceivers. In someembodiments, the present invention is not so limited and adjusting orsteering of the one or more transceivers and/or one or more antennas mayprovide proper alignment of the communication pathway. The determinationof the satellite's trajectory, orientation and/or position may be basedon aligning with the closest approximation of the optimal pathwaybetween the terminals. Operation 1250 launches the satellites into orbitand their orbital positions coordinated such that they pass in thevicinity of the closest approximation of the optimal pathway, andtherefore minimizing latency and variability in latency during datatransfer. After data has reached an endpoint at either terminal, it maythen be delivered to an end user location, such as, e.g., a financialservices server or a terrestrial communication network.

In some embodiments, the communication relay system may be configured tobe scalable and/or reconfigurable, such that individual satellites of aconstellation in orbit can be added, removed, re-oriented and/orre-positioned while maintaining continuous connectivity between theterminals. The system may also be configured to comprise extra orredundant satellite nodes or communication paths, such as used to makenew connections before old ones are dropped in order to maintaincontinuous connectivity as the satellites orbit around the earth. Forexample, a satellite can be added into an existing orbital plane andconnected to neighboring satellites by the transceiver's steeringcapability.

In at least one embodiment, the present invention discloses a system anda method for establishing a communications pathway along a multi-linkfree-space path comprising continuously moving nodes that may be basedsolely on geographic location information of the source and destinationpoints, instead of information about nodes outside of the geographicregion of the free-space path, content or metadata, such as, e.g., date,time, headers of the information content, destination addressinformation, and other information that may permit the destination to besearched, or which may require analysis or interpretation of theinformation content. The pathway may be predetermined in position andorientation, and therefore, the nodes may be active based on geolocation data, e.g., GPS, as opposed to legacy systems that inspect thedata and in real-time determine the optimum path to send the data to theending destination. In one embodiment, the communication pathway maymimic a fiber cable wherein data may enter one end of this data channelexit the other end of the data channel without any hindrances. Becauseof the predefined data channel in our implementation and thepredictability of the orbit hand-offs, data transfer predictions can beused to minimize the variability in the latency without any knowledge ofthe data content.

All prior attempts at laser communication in space have used anoptical-to-electrical-to-optical (O-E-O) approach, with the incomingoptical signal converted to an electrical signal, and then convertedback to an outgoing optical signal. This may have the advantages thatthe signal can undergo a full re-amplification, re-shaping and re-timing(3R) regeneration on-board while it is in the electrical domain, but thesize, weight, and particularly power of the hardware may be a severechallenge. In addition, due to the additional processing steps requires,additional latency may be introduced to the system. Much of the work hasalso concentrated on using satellites in GEO, for which the range ismuch farther than the MEO and LEO satellites.

The system and the method of the present invention may optically forwarddata onto the next satellite in an adjacent orbital plane in thecommunication pathway until it reaches the last satellite, which may beclosest to the destination terminal, without converting the opticalsignals into electrical signals, and thus, without analyzing informationabout satellites outside of the free-space path or regard to determiningcommunication content. In other words, data entering a geographicallydefined region in space at one satellite is simply retransmitted to thenext satellite with only possibly signal conditioning which avoidsintroduction of latency or signal propagation delays from analysis ofsignal content, or transduction of the communications signal from oneelectromagnetic form into another electromagnetic form that introduceslatency or signal propagation delays as the data is passed on to thenext node in the geographically defined region in space, e.g., withinthe communication path or channel. This approach is used to reduce oreliminate delays introduced into a communications chain due totraditional processing of data to establish a routing path, such as,e.g., analyzing, interpreting, compressing, and encrypting or decryptingelements of the communications data to determine how to forward the dataalong the chain of moving nodes based on content in the data, e.g.,destination address information or such as analyzing relative positionsand orientations of satellites to determine if path changes are requiredbased on changes in relative position and orientation. The data sequencemay be amplified or the signal electrically conditioned, such as, e.g.filtered to remove noise, but it is not processed in any fashion thatevaluates or uses content to make decisions. In addition, downlinking ofthe data being communicated to the destination terminal from the lastsatellite may also be performed independent of communication content ortraffic information, and may be based on the geographic locationrelative to the destination terminal and/or electromagnetic visibilityof communication devices that are at the destination.

FIGS. 13A-B depict flow diagrams for determining satellite datatransmission, according to at least one embodiment. In FIG. 13A,operation 1310 may determine whether a satellite is in a nominal state.If the satellite is not in a nominal state, communications payload datatransmission may not be enabled; operation 1320 may disableinter-satellite data link. However, if the satellite is in a nominalstate, then operation 1330 may determine whether the satellite's orbitallocation is within a communication boundary box. If the satellite is notwithin a communication boundary box, then communications payload datatransmission may not be enabled; operation 1340 may disableinter-satellite data link. However, if the satellite is within acommunication boundary box, then operation 1350 may enableinter-satellite data link. In some embodiments, the method may repeat.

In FIG. 13B, operation 1360 may determine whether a satellite is in anominal state. If the satellite is not in a nominal state,communications payload data transmission may not be enabled; operation1370 may disable ground to space data link. However, if the satellite isin a nominal state, then operation 1380 may determine whether thesatellite's orbital location is within a communication boundary box. Ifthe satellite is not within a communication boundary box, thencommunications payload data transmission may not be enabled; operation1290 may disable ground to space data link. However, if the satellite iswithin a communication boundary box, then operation 1399 may enableground to space data link. In some embodiments, the method may repeat.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the claimed invention. In addition, the logicflows depicted in the figures do not require the particular order shown,or sequential order, to achieve desirable results. In addition, othersteps may be provided, or steps may be eliminated, from the describedflows, and other components may be added to, or removed from, thedescribed systems. Accordingly, other embodiments are within the scopeof the following claims.

It may be appreciated that the various systems, methods, and apparatusdisclosed herein may be embodied in a machine-readable medium and/or amachine accessible medium, and/or may be performed in any order. Thestructures and modules in the figures may be shown as distinct andcommunicating with only a few specific structures and not others. Thestructures may be merged with each other, may perform overlappingfunctions, and may communicate with other structures not shown to beconnected in the figures. Accordingly, the specification and/or drawingsmay be regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A communication system, comprising: one or moresatellites disposed in one or more orbital planes; at least twoterminals positioned at end sections of a plurality of satellites,wherein the plurality of satellites are configured to providebi-directional communication between the two terminals, wherein datatransmission between the terminals is based solely on geographic data ofthe terminals, wherein the terminals are located at or above apredetermined minimum latitude, and wherein the earth's circumference isinversely proportional to latitude.
 2. A communication system,comprising: one or more satellites disposed in one or more orbitalplanes; at least two terminals positioned at end sections of a pluralityof satellites, wherein the plurality of satellites are configured toprovide bi-directional communication between the two terminals, whereindata transmission between the terminals is based solely on geographicdata of the terminals; an optimal pathway comprising a theoreticalpathway that is determined based on transmitting and receivingsatellites' position and orientation, distance, and electromagneticvisibility, and wherein the theoretical pathway travels in the east orthe west direction when it is highest in latitude.
 3. A communicationsystem, comprising: one or more satellites disposed in one or moreorbital planes; at least two terminals positioned at end sections of aplurality of satellites, wherein the plurality of satellites areconfigured to provide bi-directional communication between the twoterminals, wherein data transmission between the terminals is basedsolely on geographic data of the terminals; an optimal pathwaycomprising a theoretical pathway that is determined based ontransmitting and receiving satellites' position and orientation,distance, and electromagnetic visibility, wherein the theoreticalpathway travels generally in the north or south directions when it isbelow a predetermined latitude, and wherein the theoretical pathwaytravels generally in the east or west directions when it is above thepredetermined latitude.
 4. A communication system, comprising: aconstellation of satellites fixed in position and orientation disposedin a plurality of orbital planes; an optimal pathway comprising atheoretical pathway; an algorithm-generated boundary box within whichtransmission between a satellite and a terminal, or any combinationthereof, is permitted, wherein data transmission between the satelliteand the terminal, or any combination thereof, does not compriseprocessing nor analysis of the data, wherein edges surrounding theboundary box comprise maximum latitudes and longitudes permitted in acommunication pathway, and wherein edges of the boundary box compriseslongest permitted pathways.
 5. A communication system, comprising: aconstellation of satellites fixed in position and orientation disposedin a plurality of orbital planes; an optimal pathway comprising atheoretical pathway; an algorithm-generated boundary box within whichtransmission between a satellite and a terminal, or any combinationthereof, is permitted, wherein data transmission between the satelliteand the terminal, or any combination thereof, does not compriseprocessing nor analysis of the data, and wherein latitude edges of theboundary box decrease and approach the optimal pathway when additionalsatellites are added to the constellation.
 6. A communication system,comprising: a constellation of satellites fixed in position andorientation disposed in a plurality of orbital planes; an optimalpathway comprising a theoretical pathway; an algorithm-generatedboundary box within which transmission between a satellite and aterminal, or any combination thereof, is permitted, wherein datatransmission between the satellite and the terminal, or any combinationthereof, does not comprise processing nor analysis of the data, whereinthe theoretical pathway comprises a change in north-south direction thatis greater than the change in east-west direction when it is below aminimum threshold latitude, and wherein the theoretical pathwaycomprises a change in east-west direction that is greater than thechange in north-south direction when it is above the minimum thresholdlatitude.
 7. A communication system, comprising: a constellation ofsatellites fixed in position and orientation disposed in a plurality oforbital planes; an optimal pathway comprising a theoretical pathway; analgorithm-generated boundary box within which transmission between asatellite and a terminal, or any combination thereof, is permitted,wherein data transmission between the satellite and the terminal, or anycombination thereof, does not comprise processing nor analysis of thedata, wherein multiple alternate pathways transmit overlapping databetween the terminals for preventing a gap in transmission and aconfirmation of data, wherein the alternate pathways transmit theoverlapping data in at least one of a different frequency and adifferent polarization, and wherein duplicate data converges at areceiving satellite or terminal and is removed by the receivingsatellite or terminal.
 8. A communication system, comprising: aconstellation of satellites fixed in position and orientation disposedin a plurality of orbital planes; an optimal pathway comprising atheoretical pathway; an algorithm-generated boundary box within whichtransmission between a satellite and a terminal, or any combinationthereof, is permitted, wherein data transmission between the satelliteand the terminal, or any combination thereof, does not compriseprocessing nor analysis of the data, and wherein an actual pathway takenis the most accurate approximation of the optimal pathway at any giventime.